Colorectal rectal cancer (CRC) is the third most common cancer in the US with over 50,000 individuals dying annually from the disease. Despite multiple effective screening tests, CRC screening remains underutilized relative to other cancer screening. A driving factor behind this underutilization among insured populations is the gap that exists between a physician recommendation for care and the patient's receipt of screening. How best to support patients in CRC screening once they have a physician recommendation for care remains unknown. The proposed project will test the effectiveness and impact of a post-visit, patient portal tool, e-Assist, for engaging and supporting primary care patients in their decision making regarding, and ultimately in their obtaining, CRC screening. The tool purposely leverages the cue to action provided by a physician recommendation for care as well as the secure patient portal platform now commonly found within primary care practices. It seamlessly combines important patient-physician decision making content with assistance in removing personal and structural barriers to screening. Our research will answer four overarching questions: (1) Can a post-visit, patient portal tool, e-Assist, increase adherence to physician-recommended CRC screening? (2) How does e-Assist engage primary care patients in the CRC screening decision making process? (3) Are there subgroups of the primary care population for whom e-Assist is more engaging and effective? and (4) What adaptations are needed to e-Assist to improve its reach, and ensure its adoption, implementation, and ultimately its impact on evidence-based CRC screening use among diverse primary care patients and clinics? These questions will be addressed using a two-arm, practical randomized trial supplemented with findings from focus groups and in-depth interviews with patients, clinicians and other clinic staff to ensure a comprehensive understanding of not only program effectiveness and implementation, but the factors driving overall program impact. Results will illustrate how e-tools can be used following an office visit to support both patient decision making, and the dissemination and implementation of evidence-based cancer screening services in primary care.